i posted not too long ago about my leaky valve cover gaskets. its a common thing that seems to roughly wear out. i paid 330 (or so i think) to get mine done a few months ago. it makes you feel a lot better when you dont smell burning oil when you are near your car. the rear bank is hard to get to and there are numerous posts on how-to's and such all over the forum. what kind of miles are on your engine? id say save yourself the headache and just take care of it.
My old post
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i just got both of my banks done at firestone for 330 +/- i dont remember off hand, but in that ball park. again that was for BOTH FRONT AND REAR BANKS. when he quoted me that i did it right then and there. i was out talking with the mechanic and the rear bank was a major hastle to get at especially if you dont have the proper lighting and tools. i was leaking oil from my rear valve cover gasket and was going to put it off but i couldnt stand getting into a
car that smelled like it was burning oil. i was very pleased to say that after much worry about sludge my motor was even cleaner than the pictures

just been changing the oil fairly regularly, also i thrown in the occasional oil thickener, and a can of restore has been through the oil system.
id do it again in a heartbeat. (despite the fact i needed the repair) couldnt beat the price for ease of mind and a clean running car.
Edit: it was a 3 hour job that took about all three hours.